1. Field of the Invention
The present invention relates to vehicle travel safety devices for preventing a vehicle from colliding with an oncoming vehicle by using an object detecting means such as a radar device.
2. Description of the Prior Art
Such a vehicle travel safety device is already known from Japanese Patent Application Laid-open No. 7-14100.
In the above-mentioned publication, the possibility of a collision of a vehicle with an oncoming vehicle is determined on the basis of the distance between the vehicle and the oncoming vehicle, the relative speed between the vehicle and the oncoming vehicle, the vehicle speed of the vehicle and the image in front of the vehicle, and in the case where there is a possibility of a collision, the collision is avoided by alerting the driver with an alarm or by carrying out automatic braking.
In the case where there is a possibility of a collision between a vehicle and an oncoming vehicle, consideration can be given to avoiding the collision by carrying out automatic steering instead of automatic braking or in addition to automatic braking. In such a case, since the vehicle attitude of the vehicle is disturbed due to automatic steering being used, the driver is forced to perform an operation to return the vehicle attitude to its original state, and thus there is the problem that the driver receives an operational burden and an uncomfortable feeling.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to reduce the operational burden and the uncomfortable feeling given to the driver by automatically restoring the disturbance in the vehicle attitude of the vehicle caused by the collision avoidance control when avoiding a collision between the vehicle and an oncoming vehicle by means of automatic steering.
In order to achieve the above object, there is proposed a vehicle travel safety device comprising an object detecting means for detecting an object present in the direction in which a vehicle is traveling, a vehicle speed detecting means for detecting the vehicle speed, a relationship calculating means for detecting an oncoming vehicle on the basis of the result of detecting by the object detecting means and the vehicle speed of the vehicle detected by the vehicle speed detecting means and for calculating the relationship between the vehicle and the oncoming vehicle. A collision determining means determines the possibility of a collision between the vehicle and the oncoming vehicle on the basis of the relationship calculated by the relationship calculating means, an actuator steers the vehicle, and an actuator control means controls the driving of the actuator when it is determined by the collision determining means that there is a possibility of a collision. The driving of the actuator includes a lateral movement control for moving the vehicle laterally in order to avoid the collision between the vehicle and the oncoming vehicle and a yaw angle correction control to return the vehicle attitude of the vehicle after the avoidance of the collision, to the state the vehicle attitude was in prior to the avoidance of the collision.
In accordance with this arrangement, when it is determined that there is a possibility of a collision between the vehicle and the oncoming vehicle, since the actuator control means controls the driving of the actuator to move the vehicle laterally, a collision with the oncoming vehicle can be avoided reliably even in the case where the driver does not spontaneously carry out an operation to avoid the collision. Moreover, even when the vehicle attitude of the vehicle is disturbed due to the lateral movement control by the actuator, since the vehicle attitude of the vehicle is returned to the state it was in prior to the avoidance of the collision by controlling the actuator using a yaw angle correction, the vehicle attitude can be automatically restored to its original state and the operational burden and the uncomfortable feeling given to the driver can be reduced.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the collision determining means determines the possibility of a collision on the basis of a comparison between a correct route by which the vehicle can correctly pass the oncoming vehicle and a predicted collision position at which the vehicle is presumed to collide with the oncoming vehicle.
In accordance with this arrangement, since the possibility of a collision is determined on the basis of a comparison between the correct route via which the vehicle can correctly pass the oncoming vehicle and the predicted collision position at which the vehicle is presumed to collide with the oncoming vehicle, it is possible to accurately determine the possibility of a collision between the vehicle and the oncoming vehicle.
Further, in accordance with the invention, there is proposed a vehicle travel safety device comprising a vehicle yaw rate detecting means for detecting the yaw rate of the vehicle, and the vehicle attitude is detected by integrating the yaw rate detected by the vehicle yaw rate detecting means from the point at which the lateral movement control is started.
In accordance with this arrangement, by integrating the yaw rate of the vehicle from the point at which the lateral movement control is started, the yaw angle of the vehicle, that is to say the vehicle attitude of the vehicle, can be detected accurately. Moreover, by setting the initial value for the yaw angle to zero (0) at the point at which the lateral movement control is started, the influence of drift in the yaw rate detecting means can be eliminated to enhance the precision with which the yaw angle of the vehicle is detected.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the yaw angle correction control is carried out in order to converge the integral value of the yaw rate to zero (0).
In accordance with this arrangement, by carrying out the yaw angle correction control to converge the integral value of the yaw rate to zero (0), after the avoidance of a collision, the vehicle attitude can be returned exactly to the state it was in prior to the avoidance of the collision.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the yaw angle correction control is started at a predetermined time before the completion of the lateral movement control or at a predetermined time after the start of the lateral movement control.
In accordance with this arrangement, since the yaw angle correction control is started at a predetermined time before the completion of the lateral movement control or at a predetermined time after the start of the lateral movement control, a collision can be avoided effectively by effective liaison between the lateral movement control and the yaw angle correction control and the vehicle attitude can quickly be returned to the state it was in prior to the avoidance of the collision, without giving the driver an uncomfortable feeling.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the lateral movement control is completed in a predetermined time after it has started.
In accordance with this feature, the lateral movement control is carried out over a predetermined period, and the lateral movement control can be prevented from being carried out rapidly thus changing the vehicle attitude suddenly.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the yaw angle correction control is completed in a predetermined time after it has started.
In accordance with this arrangement, since the yaw angle correction control is completed in a predetermined time, endless continuation of the yaw angle correction control causing the driver to receive an uncomfortable feeling, can be prevented.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the driving force of the actuator in the yaw angle correction control is set to be smaller than the driving force of the actuator in the lateral movement control.
In accordance with this arrangement, since the driving force of the actuator in the yaw angle correction control is set to be smaller than the driving force of the actuator in the lateral movement control, inhibition of the smooth lateral movement of the vehicle can be prevented, and thus any uncomfortable feeling given to the driver can be reduced.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the amount of drive of the actuator in the lateral movement control is set so that the amount of lateral movement of the vehicle based on the amount of drive is not higher than a predetermined level.
In accordance with this arrangement, since the amount of drive of the actuator to automatically avoid an oncoming vehicle is restricted not to be higher than a predetermined level, the vehicle can be prevented from drifting off the road due to too large an amount of lateral movement of the vehicle.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the amount of drive of the actuator in the lateral movement control increases as the direction in which the vehicle is traveling approaches the oncoming vehicle.
In accordance with this arrangement, since the amount of drive of the actuator in the lateral movement control increases as the direction in which the vehicle is traveling approaches the oncoming vehicle, a collision can be avoided reliably by generating a large amount of lateral movement when there is a high possibility of a collision.
In accordance with the invention, there is proposed a vehicle travel safety device wherein the lower the vehicle speed of the vehicle, the larger the amount of drive of the actuator in the lateral movement control.
In accordance with this arrangement, since the lower the vehicle speed of the vehicle the larger the amount of drive of the actuator that is needed in the lateral movement control, when there is a high possibility of a collision the collision can be avoided reliably by carrying out the lateral movement with good responsiveness.